As a packaging material for packaging foods, pharmaceutical and medical products and groceries, a four-side-sealed packaging bag is known. Such a four-side-sealed packaging is provided by sealing two base films of a quadrangular bag body at four sides. The packaging bag has four sharp corners, which may hurt a hand or make runs in stockings and the like. Accordingly, a technique to cut the four corners in a substantially arc shape has been widespread.
For a manufacturing device of a packaging bag, an outline process in which devices are individually operated and an inline process in which devices are incorporated in a process line to manufacture a roll of packaging bags are available.
In the outline process, as shown in FIG. 10A, after sealing side seal portions 21 and a bottom seal portion 22 to form a quadrangular three-side-sealed packaging bag 1A, corners 11 on the side seal portions 21 and the bottom seal portion 22 are cut in two steps to form a packaging bag 1. Alternatively, as shown in FIG. 10B, after sealing the side seal portions 21 and the bottom seal portion 22 to form a quadrangular three-side-sealed packaging bag 1A, corners 11 on the side seal portions 21 and the bottom seal portion 22 are cut in one step to form a packaging bag 1. This outline process is time-consuming because of manual cutting and considerably costly because heavy equipment investment is required for using expensive machines.
In the inline process, as shown in FIG. 11A, in a base film 10 having a partition 181 sealed at every predetermined distances and partition 182 continuously sealed at one side, a part (chip 12) of the partition 181 is firstly cut off to form a rounded portion 13. Subsequently, the base film is cut along a straight line L located near a center part of the partition 181. As shown in FIGS. 11B and 11C, as a result of such a two-step operation, the straight line L and an end of the rounded portion 13 are not aligned to unfavorably form a protrusion P.
Accordingly, according to a technique, two cutting lines are provided and are respectively cut with two blades, thereby avoiding protrusion formation.
As disclosed in Patent Document 1, another technique using a blade capable of integrally forming four corners and a straight line of a packaging bag and cutting the four corners and the straight line in a one-step operation is also known.
[Patent Document 1] JP-A-05-8330